


shut the door

by murcielag0



Category: Haikyuu!!
Genre: Accidental Voyeurism, Brother/Brother Incest, Canon Compliant, Incest, Late Bloomer, M/M, Mildly Dubious Consent, Miyacest Exchange 2021, Porn With Plot, Puberty, Sibling Incest, Twincest, Underage Masturbation, hints of dacryphilia, knowledge gap, sexual awakening, sexual initiation, slight power imbalance
Language: English
Status: Completed
Published: 2021-02-26
Updated: 2021-02-26
Packaged: 2021-03-14 19:01:27
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 6,527
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29546931
Author URL: https://archiveofourown.org/users/murcielag0/pseuds/murcielag0
Summary: Atsumu and Osamu may have had their growth spurts at the same time, but that doesn't mean every change or new discovery happens to them at the same rate—or in exactly the same way.
Relationships: Miya Atsumu/Miya Osamu
Comments: 17
Kudos: 233
Collections: Miyacest Gift Exchange





	shut the door

**Author's Note:**

  * For [tajemnica](https://archiveofourown.org/users/tajemnica/gifts).



> Written for the Miyacest server's Valentine's Day exchange. 
> 
> Prompts were: Underage, PWP. (There's some plot in here, hope you don't mind.)

#### shut the door

  
  


The middle school summer drones on and on like endless cicadas, the golden sun high in the sky beating down on the back of the twins’ necks while they practice volleyball in the backyard until the ball slips from their fingers from all the sweat.

They’ve been at it for a good number of hours, nonstop egging each other on in one drill or another. Their tank tops are stuck to their bodies like the hair on their foreheads, parted in mirror image. They have water bottles to drink from, but after Osamu retrieves the lost ball, he says he’s going inside. Atsumu shrugs but doesn’t respond—he catches the ball, shakes the salt from his hair, and lays down in the grass to practice on his own, tossing the ball high in the air, its round shadow blocking the orb of the sun like an eclipse.

Atsumu slips into a sort of trance, focused on the way the ball lands on his fingertips and the bend of his elbows as he tosses it as high as he dares. How long can he keep it up? How long can he ignore the burn in his muscles? How many tosses in a row can he complete?

Eventually, the ball misses his hands, or his hands miss the ball, and it bounces out of his reach and rolls down the grass to the edge of the house.

"Stupid wind," Atsumu groans, and rolls up to his feet. He stops to take a drink, but the water bottle is so warm in his hand he doesn’t bother, just heads to retrieve the ball and go inside where he can cool off and get some ice.

Atsumu comes in through the side door to the laundry and storage area, putting the ball away and stripping off his sweaty tank, which he tosses in the dirty clothes hamper by the washer—he knows better than to let Ma find it in a heap somewhere.

Inside, the house is so much cooler Atsumu shivers once on the way to the kitchen. He splashes his face, then pours himself a tall drink of cold water, gulping it down. He refills the glass and adds some ice, then realizes the house is quiet. Too quiet.

Atsumu smirks. Osamu's obviously up to something. The living room is empty, the TV turned off, game controllers where they left them that morning. Atsumu tip-toes down the hall, careful not to let the ice cubes clink against the glass.

The bathroom they share smells like shampoo and steam, so he guesses Osamu took a shower. Atsumu sniffs his armpits and makes a face; he's not used to smelling so bad after a little practice. He could probably use a shower too.

The door to their bedroom is half closed. Atsumu moves silently, slowly peeking around the edge to see what his brother is up to, grinning and eager to catch him unawares.

Osamu's sprawled out on his back in his bunk, hair wet and towel discarded on the floor. He's got his earbuds in and is watching something on his phone.

But that's not what seizes the breath inside Atsumu's throat.

For some reason, Osamu's hand is touching his dick—fingertips tracing up the underside where it rests on his stomach. And there's something wrong with it—it's… all puffed up. Double the size—triple?

Atsumu gasps. The hell? Is Osamu hurt? Did he get stung by something outside?

But Osamu doesn't look like he's hurting or uncomfortable while touching himself. He _keeps on_ touching himself, closes his hand around his dick and rubs along the surface. 

Atsumu can see how thick it is, how stiff when held in his brother's palm, while the rest of him is naked there in the bed, a thin trail of hair below his navel, and on his sack, and down his calves. It’s just like when Atsumu's grew in, but he hasn't really paid attention or seen his brother fully nude like this in a long time and somehow the sight feels illicit, like he shouldn't be seeing him this way… and shouldn't _want_ to, but he can’t seem to stop.

Osamu tugs the swollen thing between his legs, works it so the foreskin peels back and reveals the glistening head, dewy and pink. Then he strokes upward and it's covered up again with skin and fingers. Every motion up and down makes the pink peek back out again. Atsumu swallows, chest tight, skin hot, heart beating so fast he's not sure what's going on—alarm bells clanging between his ears.

What is this? He's never _seen_ anything like this—seen anyone doing anything like _this—_ but he knows better than to reveal as much or he'll be ridiculed without mercy. He can’t get caught like this, he wants to look away, but he _can't._

Osamu's hips start moving too, thrusting up into his grip as he lets out this low, guttural moan that prickles the hair on Atsumu's neck, his arms, his legs, his—oh god, his balls are tingling and _that's_ weird and he grabs them to make it stop but— _fuck!_ His dick—his dick is starting to stiffen up—why’s it doing that? Osamu's moans and the sounds of his hand doing _that—_ he’s got goosebumps again, something's wrong, he feels _wrong._

Osamu groans, rolling his hips, and Atsumu's dick _twitches_ , and fuck—his heart is racing so fast he might die—what's happening to him? He doesn't dare let go of his balls but he's trembling, the water glass is slipping, and tears start to pool at the corners of his eyes, he's on fire and doesn't know how to make it stop.

Osamu's hand is flying now, really going to town over his strangely large dick, and fuck—stuff is leaking from the pink tip every time it flashes into view, dripping out onto Osamu's fingers like popsicle juice melting in the sun after school only this stuff is clear and syrupy.

The longer Atsumu watches the more he can feel his dick jumping in his shorts and a burning feeling grows in his stomach, agitating him till he closes his legs around the fist holding his balls, but it's not stopping, he can't breathe, he needs help—

Atsumu shoulders the door open and waddles into the room before collapsing on his knees and dropping the glass of water. _"Samu!"_

Osamu yanks out his earbuds and whirls to face him, a look of horror contorting his face. 

"Samu!" Atsumu whines again, tears spilling over as Osamu's eyes stare at where Atsumu's hands are gripped between his legs.

"Do ya _mind?"_ Osamu shouts, sitting up abruptly and kicking the towel on the floor closer to the spill. "The fuck are ya doin' comin’ in here?"

"I don't _know,_ something's wrong!" Atsumu sniffs through his tears.

Osamu grabs for his boxers at the foot of the bed and looks at him in disgust, his dick noticeably deflated. He seems so angry—maybe it hurts? 

Atsumu's dick feels horrible too and a wave of humiliation washes over him. He sobs and bends forward to hide himself even more. He squints his eyes shut, and says meekly, "Help me?"

Osamu stomps towards the door. "Figure it out yerself!"

 _"Wait!"_ Atsumu makes a desperate grab for Osamu's ankle, but Osamu kicks his hand away.

 _"Don't_ touch me!" Osamu shouts, making his escape through the doorway and stomping through the house to the side door. 

There's a rustling of the clean clothes hamper by the dryer, then a stamping of sneakers on bare feet.

"Tell Ma I'm at Aran's!" Osamu calls over the sound of the side door opening.

Atsumu sits up, a chill of panic striking through him. _"Samu!"_

He hears the side door slam, and the panic is like an electric shock. 

"Samu, don't leave me!" He wails.

The water on the floor has pooled into Atsumu's leg, and he breaks down in sobs. 

"Samu, don't leave me!" he shouts again, feeling somehow betrayed and also devastated. It's overwhelming.

He reaches for the towel and starts wiping the floor one-handed, calling for his brother between heaving sobs, and knowing that Ma will be very upset if she finds the floor damaged while she was at work. 

Osamu ignores his brother’s wailing and grabs his bike, heart pounding in his chest. 

_Fuck._

He didn't expect to get caught like that. All he can think to do is get as far away from his brother as possible, and pray that Atsumu didn't see the damning video on his phone that was fueling his attempted jerkoff session. 

He walks the bike around the side of the house to their street, but some of the windows in the house are cracked for ventilation and he can still hear the muffled sounds of Atsumu calling out for him and sobbing. 

He slows to a stop. That over-sensitive moronic _baby._ Probably has snot all over his face.

Osamu grinds his teeth. It's so frustrating. He didn't even get to come, and now those helpless noises are working him up all over again, making him hot under the collar. Can't even have five minutes of privacy to take care of shit.

Then the wave of guilt. Always there, coiled around him and settling heavy in his gut. He doesn't know why he's like this, half hard over his brother's ugly tears. Taking photos of him, or videos of him at practice or getting changed, piling up the evidence of his twisted desires. Wanking to his secret collection and feeling sick at how good he feels during and after. 

He feels a little bit guilty for freaking Atsumu out, and leaving him a mess, dramatic shit that he is. Ma's gonna be so pissed if she comes home and finds Atsumu red-eyed from crying all day while she's at work. 

What if Atsumu spills to her what he was doing? Fuck! 

Osamu scowls and turns the bike around, parking it by the side door and going quietly back inside to check on Atsumu. Hopefully he can at least get him to stop blubbering.

Osamu creeps through the house and finds Atsumu still in their bedroom, toweling ineffectually at the water spill and sniveling. 

He gently pushes the door open. "Are ya alright?"

Atsumu whips his head around, gawping, eyes wet with tears. Then he turns away, cowering over his closed knees. 

"Thought yer goin' to Aran's."

Osamu recognizes that petty tone under the hurt. "Dummy. Can't leave ya when yer worked up like this. The hell's goin' on, 'Sumu? Pull a muscle or somethin’? Hurt yerself somewhere?"

"I don't know!" Atsumu snaps, whirling to face him. "It's all yer fault!"

Osamu wants to go right on the defensive, but he takes a breath and lets it out. "Look. Thought I'd finish before ya came in. Sharin' a room it's bound to happen, so stop actin' all traumatized. Could just as easily’ve been me bargin' in on ya."

"Ya don't get it!" Atsumu wails, doubling over again. "I don't do stuff like—like _that—_ there's somethin' really wrong with me!"

"Whatcha mean?" Osamu stares at his brother's sweaty back, perplexed. 

"It hurts and I dunno how to make it stop!" Atsumu's tears start up again and Osamu sighs, crouching on the floor next to Atsumu. 

"Show me what hurts," he says.

Atsumu cringes away from him.

Osamu glares. "I can't help ya if I don't know what's wrong!"

Atsumu tsks, and looks away, obviously conflicted. For a moment Osamu's stomach sinks with dread, wondering if he's going to have to take Atsumu to the hospital or something. Maybe he cut himself doing something stupid. Maybe—fuck, he does _not_ want to get in trouble for this. 

"I can't," Atsumu says softly.

"Whatcha mean ya can't?" Osamu presses.

"I mean I can't let go, Samu," Atsumu sniffs. "I dunno what's gonna happen if I do."

Osamu slides around to face the stubborn set of Atsumu's shoulders. Both his brother's hands are cupped tight between his legs. Osamu's stomach tightens, a lick of flame rekindling his desire at the sight of Atsumu so… pitiful, there on the floor, gripping his crotch. Osamau swallows, curling his fingers against the urge to touch him, make him reveal whatever he’s hiding.

"What, gotta pee?" He says instead.

 _"Samu!"_ Atsumu whines, turning away again. “Not that!” Then, softly, "It won't go down."

Osamu inhales sharply. Oh fuck. His brother's got a hard-on. Right there in front of him. In their room. With no one home. Asking for his _help._

His hands start to sweat. "It'll go down if you stop touching it," he says.

"I tried that!" Atsumu growls, shifting his knees. "Didn't work, there's something wrong!"

"Then ya gotta jerk it all the way," Osamu says. 

"But it hurts!" Atsumu insists, visibly frustrated. He turns his head, cheeks and neck coloring an embarrassed red. "And anyways, I dunno how to—what yer tellin' me."

Osamu licks his lips, heart thudding out of rhythm from the eagerness welling up inside him. "Ya never did it before?" He asks, feigning calm.

"So _what?"_ Atsumu bares his teeth. "Ya don't hafta get all high an' mighty—"

"—Shut up a second!" Osamu gruffs. "Look, can ya get up?" 

"I don't know!" Atsumu shouts, but his bravado crumples around the edges.

"Then I'll help ya," Osamu says, reaching for his brother's arm.

Atsumu jerks away. "Ya said not to touch ya!"

"Forget that, didn't mean it," Osamu replies. "C'mon. At least sit up on the bed."

Atsumu's eyes widen. "... Yer gonna let me on your bed?"

Osamu's desires surge again, pooling in his gut. There's a reason he stopped letting Atsumu into his bed. The same reason he's helping him onto it now, palms sweaty and heartbeat speeding up in his chest.

"This time, okay? Get up there before I change my mind," he says, helping Atsumu get his feet under him by lifting him up by the armpits.

With Osamu's hands to steady him, Atsumu shuffles to the bed while holding his crotch, then sits down all at once. 

"Lie back," Osamu intructs.

Atsumu gives him a look.

"Trust me," Osamu says, another lick of flame under his skin twined with a pang of guilt.

Atsumu scoots back and then stretches out on the bunk bed, hands still tightly protecting his junk. Osamu waits to see if he will let go, but Atsumu doesn't. So Osamu stretches out next to him, real slow, watchful.

"What are ya doin'?" Atsumu asks, nervous.

"Gonna help ya, like ya asked." He pushes Atsumu's hair off his sticky forehead, and Atsumu sighs, biting his lip. Then Osamu adds, “Duh,” and pinches Atsumu's nose and sticks out his tongue.

"Just help me already, jeez!" Atsumu huffs.

Osamu shifts closer. He touches Atsumu's wrist, and then strokes down to Atsumu's trembling hands. "Let me see."

Atsumu turns his face away, but slowly moves his hands from his groin. Osamu sees his brother's partially erect dick under his shorts.

"Yer only halfway hard," Osamu comments, rubbing Atsumu's wrist. "Can either let it go down on it's own or ya can speed it up. Whatcha want?"

"Speed it up," Atsumu says immediately. "I don't wanna feel like this anymore, Samu." He gets teary again, breathing hard, and Osamu is quick to brush the wet off his cheeks.

"First ya have to show it to me," Osamu says. He reaches for Atsumu's chest, still sweaty from practicing out back, but hesitates. He swallows, then places his palm on Atsumu's stomach, seeking to comfort him.

Atsumu arches his back at the touch, and Osamu doesn't miss how his brother's dick jumps under his shorts. 

"Samu—" Atsumu cries.

"Take yer shorts down," Osamu says, more impatiently. 

"What? Why?" Atsumu snaps to attention.

"Because ya gotta touch it if ya want it to go down!" Osamu shouts.

"I can't do that!" Atsumu protests, curling away from him towards the wall. 

"Then whaddya expect?" Osamu huffs, exasperated. "Can't show ya if ya don't touch yerself—"

_"—You do it."_

Osamu bites his lip. "Huh?"

Atsumu folds his arms around his chest, staring at the wall. "Will ya just do it?" He repeats, soft and unsure. 

Osamu sucks in a breath, looking up at the underside of Atsumu's bunk and praising whatever wicked luck is at work here, putting this gift from his deepest darkest fantasies right into his bed. He clenches his fist in a tiny victory pose and then clears his throat. 

"If ya want me to, Sumu. I'll help ya out. Show ya how to get relief."

Atsumu nods, and says, "Yeah," though he still sounds a bit unsure. 

Probably nervous, Osamu guesses. Atsumu always is the first time, like the first day of school or the first day of practice with a new coach.

"Ok, Sumu." Osamu combs fingers along Atsumu's scalp, giving his hair a tousle just the way he likes, to help him relax. "Lie on yer back."

Atsumu sighs at the touch. Then he cautiously rolls over on his back, looking into Osamu's eyes. 

"Yer shorts and briefs have to come off. Help me with that, okay?" Osamu ghosts his hand over Atsumu's navel, stopping at his waistband.

When he runs a finger underneath the elastic from one hip to the other, pulling it down, Atsumu hesitantly puts his hands on either side and helps push the clothing off, lifting his body. The boxers catch on the curve of his dick, which is a little fuller now, and has clearly been leaking for a while as his underwear is completely damp on the front. Osamu finishes tugging everything down to mid thigh, gazing on his brother's dick, and the coarse dark hairs around it and covering his sack that are also shiny with precome. 

"Yer all wet," he points out, licking his lips.

"Nngh," Atsumu lets out an embarrassed squeak and tries to cover himself. But Osamu blocks him.

"Nah, it's fine. It's _good,"_ Osamu chuckles

The relief on Atsumu's face is instant, and his cheeks even turn red again. Osamu feels his chest tighten at the sight. It's cute. It's his brother, and it's wrong, but it does things to him that he wants to feel again and again, and the guilty pangs do nothing to stop his hand from gently fitting around his twin's cock.

Atsumu's hips jerk and he keens, tongue behind his teeth. Osamu's not even holding it with any strength but he freezes for a moment.

"Sumu?" He wants to be sure it doesn't hurt, remembering what Atsumu had said earlier.

Atsumu's breath is erratic as he says, "Wha—unhh—hnnn!"

Osamu tries an experimental stroke, and that produces another nice reaction from his brother, a broken moan slipping through his lips that curls Osamu's toes and sends more blood flowing between his legs.

"Go on, make any noise ya want," Osamu encourages, moving his fingers slowly but with practiced confidence. 

Atsumu scrunches up his eyes, making small, little sounds as his dick pulses in Osamu's hand, hot and filling out to full hardness until it's as big as Osamu's. Osamu gently swipes his thumb over the slit, pulling down the foreskin and exposing the pink head.

 _"Ahhhhh!_ Samu!" Atsumu cries out, shaking there on the bed. 

"Feel good?" Osamu asks, pulse racing like Atsumu’s.

"I dunno, I dunno." Atsumu turns his head from side to side, eyes closed. 

"Yer all the way hard now," Osamu says, then teases, "Thought ya'd be puny, but look how big ya got."

At this, Atsumu's eyes fly open, and he sits up on his elbows, gawking at his crotch. "Fuck! Why's it like that!"

Osamu shrugs, savoring the feel of Atsumu’s cock in his hand, thick and leaking fat drops that he collects on his fingertips. He salivates, wanting to taste—but this isn’t the time for that, his brother’s not ready. Would only freak him out.

“Just happens sometimes,” Osamu says. “Especially when yer horny.”

“I wasn't horny!” Atsumu protests, flopping back on the pillow.

Osamu frowns, hand stroking lazily over Atsumu’s cock. “So what were ya thinkin’ about?”

“I don’t know!” Atsumu shouts, throwing an arm over his eyes. “I just saw ya there… doin’ that _—doin’ this_ to yerself, and I just… I just got like this, it started hurting and I don’t know why—something’s wrong—”

“—Nothin’s wrong with ya,” Osamu cuts in, scowling. “‘S normal. Yer normal.”

Atsumu whines, fidgeting beside him.

This _isn’t_ normal at all. But with every word his brother says—how he was watching him and reacted like this—Osamu’s falling deeper. With every subtle twitch of his brother’s sweaty body he’s getting more turned on, dick straining between his legs. If Atsumu’s not normal, then _he’s_ not normal and he won’t believe that—won’t believe it’s not supposed to be like this for the two of them when Atsumu’s admitted, in his innocent way, that seeing him earlier got him hard for the first time, and how the fuck is Osamu supposed to resist that when it’s always been that way for him?

“Yer normal,” Osamu repeats, gently letting go of Atsumu’s dick. 

Atsumu looks over at Osamu, worried when he pulls away. Osamu pushes his shorts down to reveal his erection, jutting full and turgid from his hips. Atsumu’s wide eyes drop down and fasten onto his dick, so Osamu strokes himself a few times, watching the blush creep over Atsumu’s cheeks until he bites his lip. 

“See?” Osamu says, letting go for a moment so his dick is unobscured. “I’m the same.”

“The same?” Atsumu asks, frowning.

“Yeah,” Osamu says. “Watchin’ ya right now got me hard too. So it’s fine.” He resumes touching Atsumu, squeezing him carefully, and tracing the head with his thumb, almost reverently.

“It’s fine?” Atsumu repeats, thighs shifting together.

“If it’s _us,”_ Osamu amends. 

“Us?” Atsumu whispers.

Osamu ignores the sinking feeling in his core, and pushes on. “Yeah. It’s fine. Special. We’re twins, so it’s normal to make each other feel hot. It’s normal to get hard and to make each other feel good.”

It’s not. It’s _not—_ but he doesn’t care. He might never get another chance to touch him, to be with him like this.

Atsumu swallows. “You feel _good?_ Samu?”

“Yeah. Touch me too?” Osamu says, shifting closer to Atsumu’s hand lying between them on the sheets. “We can do it together. I’ll show ya.”

“But—” Atsumu chews his lip. He tentatively reaches out, brushing Osamu’s hard-on with the back of his hand.

Osamu can’t help the soft moan that slips out. He’s so _sensitive._ Partly from not finishing before. And partly because this is something he’s always wanted—no one makes him hornier or harder than his brother, twisted as it might be.

He strokes Atsumu harder, hoping to convince him to touch him back. “Like this,” Osamu says, looking into Atsumu’s eyes. “Do it like I’m doin’.”

“I don’t know if I—” Atsumu starts, but Osamu shushes him. 

“It’s easy,” he says, rocking his dick against Atsumu’s hand. “Easier than settin’.”

Atsumu exhales a laugh, lips curling. 

Osamu’s glad it was the right thing to say—Atsumu looks more relaxed. Pliant. Osamu’s lips curl in a matching small smile. 

“C’mon, Sumu,” he says, voice low. 

Atsumu looks down. His fingertips slowly rub along the side of Osamu’s dick, and when Osamu doesn’t pull away, Atsumu takes him in his hand, and then looks back up to Osamu’s face.

Osamu’s gaze is hooded, and he licks his lips. “Yeah. Good. Keep goin’.”

Atsumu’s hand is clammy, and he’s not gripping very tight, moving a little too slow. But he’s earnest about it, and Osamu hums, arching into Atsumu’s touch.

“Feels good,” Osamu says, stroking Atsumu harder and quicker until he’s oozing all over his hand and dripping onto his stomach. 

“Nnhhhnn,” Atsumu moans, rolling closer instinctively.

Osamu’s dick jumps in Atsumu’s hand, which surprises his brother enough to halt all motion.

“Don’t worry,” Osamu says, leaning closer. “Means I like it. Yer doin’ good, Sumu.”

Atsumu exhales, and he starts up again, a little more bold than before. His brows are furrowed in concentration, and Osamu bites his lip. It’s cute, he’s so cute. Fuck.

“L-like this?” Atsumu whispers.

“Yer not gonna break it,” Osamu says, thrusting into Atsumu’s fist. “Grip it like this,” he says, giving Atsumu a deliberately tight stroke that makes him gasp and squirm on his side, bucking into his hand. 

Atsumu tightens his fist and pumps Osamu’s dick harder, picking up his languid pace and sending a surge of lust tearing through Osamu. He shivers, grunting and making small thrusts into Atsumu’s fist. 

“Good, good, feels good,” Osamu says, closing his eyes. “Feels so good, Sumu.”

He’s leaking onto his brother’s hands, and Atsumu doesn’t seem to mind. Or maybe he hasn’t noticed—either way, he thinks they’re probably both getting close.

 _“Samu…”_ Atsumu pants, twitching beside him.

“Yeah, yer feelin’ it, huh,” Osamu says, twisting his wrist as he works Atsumu closer to his peak.

Atsumu whines, then grabs Osamu harder than before, enough to hurt a little more than Osamu likes. 

“Fuck!” Osamu grits his teeth, letting the sensations wash over him. He knows Atsumu didn’t mean to, and the pain brings a sort of clarity, pushing him back from the edge, so he can focus on his brother. 

“Sorry, sorry,” Atsumu cringes, pulling away his hand and rolling onto his back.

“S’okay, ya can be rough if ya want,” Osamu reassures. “Just don’t stop, Sumu, keep goin’...”

Atsumu renews his grip and continues touching him. Osamu sighs, moaning at the immediate shift from pain to pleasure. The elastic waistband of his shorts is pressing on his balls, so he lets go of Atsumu just long enough to shove his clothes down to mid-thigh like his brother’s.

Osamu licks his palm before touching Atsumu’s cock again, fisting it with purpose. Atsumu bucks, groaning, eyes fluttering closed. God, he’s so cute. So perfect. So meant for this, to be in Osamu’s bed, at the mercy of his hands. 

Osamu slides his pam down to Atsumu’s balls, caressing them gently. Atsumu whines, shaking and opening his eyes, looking so confused at what he’s feeling. 

“Like that?” Osamu murmurs, smirking. He wants to touch him everywhere. Show him _everything._

Atsumu hesitates, then nods, his dick twitching when Osamu tugs on his sack. Osamu goes back to pumping Atsumu’s cock and rocking his hips into Atsumu’s hand, noting the sweat beading on his brother’s forehead. He swallows, yearning to see his brother come even more undone as his fingers dip down to Atsumu’s balls and rub along his taint.

“Nngggh,” Atsumu whines, trying to close his legs.

“Hey, open ‘em,” Osamu says, nudging Atsumu’s thigh with his hand.

 _“Samu…”_ Atsumu complains. Osamu pushes again, and Atsumu huffs in protest but obeys, thighs widening enough for Osamu to touch his sack and taint however he wants.

Osamu shivers, relishing the access to Atsumu’s intimate areas but treading carefully. Atsumu is prone to getting overwhelmed, and Osamu definitely doesn't want that. Doesn’t want him to get scared off.

“Yer doin’ so good,” Osamu tells him. “Ya feel so good in my hand.”

Atsumu fidgets, trying to hide his face in the pillow. Osamu chuckles, watching his brother’s ears turn red. He starts jerking Atsumu off for real now, his practiced hand squeezing him just how he thinks Atsumu will like it, paying attention to his brother’s reactions.

“Unnggh,” Atsumu shifts his legs back together, tossing his head. “Samu, _Samu…”_

Osamu keeps up his frenzied rhythm, eyes blown wide at the way Atsumu writhes in the bed beside him, quivering with need. 

“Samu wait! Wait—wait, stop!” Atsumu clamps a hand on Osamu’s wrist.

“Uh-unh,” Osamu replies, shaking his head. “Yer close, I wanna make you come.”

“No—wait!” Atsumu’s nails dig into Osamu’s arm. “I’m gonna—something’s wrong, something’s wrong—”

Osamu shushes him. The hand on Osamu’s dick has stopped, just gripping him tight, like Atsumu needs it to keep grounded.

“Nothin’s wrong, Sumu,” Osamu insists. Atsumu’s dick is now granite in his hand, hot and pulsing and ready to erupt. “Yer gonna come, just let it happen—”

“I can’t—I can’t—” Atsumu wails. Osamu looks up to see tears in the corners of his brother’s eyes again, and his belly tightens. The sight fans the flames inside him, and his mouth goes dry.

“Yes, ya can,” Osamu repeats. “It’s normal, don’t fight it.”

Atsumu shakes his head. “No, no, no, I think I’m gonna piss, ‘m gonna mess the bed—”

“‘S’okay, Sumu,” Osamu murmurs. “Just let it out.”

“No, I can’t—” Atsumu tries to stop him again, and Osamu tsks.

“Yer not gonna piss, Sumu—”

“—It’s gonna come out, Samu!” Atsumu sobs, tears flowing freely now. “Ma’s gonna be so mad—”

“Shut up!” Osamu snaps, then flinches. Fuck. If _anyone_ knew—the wave of guilt makes him feel sick to his stomach. He forces the thoughts away and changes his wrist motions to grind his palm on the head of Atsumu’s dick.

Atsumu arches his back off the bed, fat tears rolling down the corners of his eyes. “Don’t wanna, don’t wanna,” he sobs. 

“Fuck,” Osamu grinds his teeth. _“Fuck—_ Sumu, ya wimp.”

Atsumu’s breath hitches on a sob, and Osamu hangs his head for a moment, hand slowing between his brother’s legs. 

“Look, just relax!” Osamu snaps.

Atsumu looks up at him, teary and pitiful, and Osamu hates the way it makes his balls quiver. He takes a deep breath. 

“Said I’d help ya,” Osamu continues more gently. “So let me help ya.” 

“It hurts,” Atsumu whines.

“Does not,” Osamu scoffs. He shifts his grip again, teasing Atsumu’s cockhead relentlessly.

“Ahhh, it hurts, it hurts,” Atsumu wails, gripping Osamu’s wrist again. 

“It hurts if ya _don’t_ come,” Osamu tells him, “So just come already!”

Atsumu groans and twitches in the bed, trying to pull his knees up. Osamu elbows them out of the way and starts stroking Atsumu’s length again. Maybe the tip is too sensitive right now?

“S-Samu,” Atsumu chokes out, tears all over his face. 

“Okay, Sumu,” Osamu answers, “Yer okay. It’s okay for ya to come, I wantcha to come.”

Atsumu inhales a shuddering breath, and then arches into Osamu’s hand.

“Yes, yeah,” Osamu eggs him on. “Like that, just thrust into my hand, however you want to do it.”

Atsumu bites his lip, eyes scrunching shut again as he bucks up into Osamu’s fist. Osamu moves with him, encouraged by the steady precome dribbling out of his brother’s slit. He slicks Atsumu’s shaft with it and then pumps him harder, the ring of his thumb and forefinger popping over the head and back down.

“Yer almost there,” Osamu says, unable to keep from thrusting his hips against Atsumu’s motionless hand at the same time.

“Nnnffffgh,” Atsumu squirms again, dick throbbing and hand squeezing Osamu’s cock tighter.

“Fuck, yes, like that,” Osamu sighs, chasing that feeling coiling in his groin. He jerks Atsumu off even faster. “Feel it build like that, in yer balls, like it’s gonna spill over.”

“Ahh, ahh, ahhhhh,” Atsumu cries out, vibrating beside him on the bed, a sheen of sweat over his skin, nipples tightened into tiny pebbles on his chest.

“Yer almost there,” Osamu says, hand flying over his brother’s dick. “Now hurry up and come _right now,_ ya big baby—”

Atsumu weeps, clamping his hand around Osamu’s dick, his free hand fisting the sheets as his orgasm ripples through his body. He screams and jerks as his cock erupts, twitching and shooting wildly in Osamu’s grip, arcs of jizz splattering all over his stomach and chest. Osamu keeps his hand moving to milk the last drops as Atsumu struggles to breathe, torso twitching and tongue pressed to the roof of his mouth from the incredible pleasure wracking through him.

It’s the most erotic sight Osamu’s ever seen in his life, Atsumu’s skin flushed rosy from ears to toes, chest and belly criss-crossed with come. 

The string of wanton noises and curses spilling from Atsumu’s throat, raspy and near-unintelligible in the aftermath of his climax tear like wildfire through Osamu and suddenly he’s coming too, spurting into Atsumu’s fist. Osamu grabs for his dick, twining his fingers with Atsumu’s and using their combined hands to pump his length and sustain his pleasure to the fullest, shooting his entire load between them, and then a final hot spurt that lands in a white streak across Atsumu’s stomach like confectioner’s icing, pooling to blend with the rest of Atsumu’s come.

When Osamu looks up, Atsumu’s watching him so intently Osamu sucks in his breath—he’s never shared this with anyone, never really thought about how he looks when he’s coming, but Atsumu’s seen it now. His brother’s seen it and felt it and heard the sounds he’s made too, little “ah’s” so similar to Atsumu’s.

 _“Sumuuu…”_ he sighs, then grunts as his dick finally softens. He slides their hands off of it, and rests them on the bed, just holding Atsumu’s hand for a moment despite how sticky they are. 

Osamu refocuses his eyes on Atsumu, whose face is bright red and whose eyes are glazed over from the rush. A lazy, satisfied smile tugs the corners of Atsumu’s mouth, and Osamu’s heart skips a beat. Fuck. They really did this.

“Felt good?” Osamu smirks.

Atsumu nods, smiling, his eyes still full of tears. He brushes them away and then holds his fist to his head, sucking in a breath that wracks through his chest. 

He seems okay… but also on the verge of being overwhelmed. There’s a weird tension now, too, and Osamu’s stomach twists with a sharp stab of guilt. They really did this, huh.

“Wait here,” Osamu says, scooting to the edge of the bed. When Atsumu looks a bit alarmed, he adds, “Be right back.”

Osamu gets out of bed and crosses quickly to the hall bathroom, grabbing a washcloth and wetting it with hot water. He wipes off his dick and thighs, then rinses the washcloth and takes it back to the bedroom.

Atsumu looks up when he enters the room, lying there in the same position as before, face pensive. Osamu sits on the bed, avoiding the wet spots. 

“Wanna clean up?” He asks, holding up the cloth. 

Atsumu nods, but makes no move to take it. So Osamu shifts closer, wiping his brother’s skin starting at his thighs, and then moving upward. 

“Sorry about yer sheets,” Atsumu murmurs, voice meek.

Osamu shrugs, glancing up. “I’ll just wash ‘em. No big deal.”

Atsumu looks relieved to hear this. Osamu continues to gently wipe Atsumu down, hoping the warmth will feel calming. It’s so intimate Osamu’s throat feels thick, and he shows his brother all the tenderness he can muster with the gentle motions of the cloth.

“Do this a lot?” Atsumu asks.

Osamu’s eyes snap up. “What? No! I wouldn’t. Not with anyone else.”

“Oh,” Atsumu says, brows meeting in a confused expression. “But, earlier—?”

Osamu realizes what Atsumu meant, and feels his cheeks heat. “Oh that. I dunno…” He thinks a moment, wiping the last of the mess from Atsumu’s chest. “Well, I jerk it pretty much daily, I guess. Sometimes more. Better than getting random boners during the day, or makin’ a mess in my sleep.”

Atsumu pales. “That can happen?”

Osamu shrugs, giving his brother a long look. “Guess ya haven’t experienced that yet?”

Atsumu shakes his head. “Think I’d remember if my dick ever....” He waves his hands vaguely.

Osamu chuckles, “Yeah, ya would. Well, now ya know how to take care of it. Once a day should prevent it. More if yer in the mood.”

“Hmmm.” Atsumu goes quiet, taking this all in. 

He smoothes a hand down his front, pausing by his navel, then lets his hand travel all the way down to his flaccid penis, cleaned off and lying inert between his legs. The gesture’s more curious than sensual, but it still makes Osamu swallow, and his pulse race. 

“Samu, ya never…” Atsumu trails off, and Osamu meets his gaze, head tilted and waiting for him to continue.

Atsumu swallows, looking away. “Ya never did this with someone else? Before?”

Osamu’s pulse spikes at the question. He considers his answer carefully, the tension in the room growing thick.

“Nah. Most people don’t. ‘S private. But—” Osamu pauses, chest thudding and palms sweating. 

Atsumu glances back at him, and Osamu steels himself. “If ya wanted to… It’s fine.”

Atsumu’s hands close, and he shifts his position. “Really?” 

Osamu shrugs. “Sure. If ya want. We’re twins,” he says, as if that answers everything. To him it does, even if that means he’s not fully normal, sick in some way nobody else would understand. 

Atsumu visibly relaxes. Osamu’s stomach swoops with guilt.

“We can’t ever tell anyone, of course,” he adds, voice serious. “It’s special. Just us.”

Atsumu nods, expression solemn. “Okay. Just us.”

Osamu remakes his bed with the freshly laundered sheets while Atsumu is taking his evening shower and brushing his teeth. He gets in his pajamas and settles in, exhausted from everything that happened earlier.

They tidied up and essentially resumed their normal habits, arguing about what to eat for lunch and then kicking each other’s asses in video games without mercy. But Osamu has a sinking feeling that it’s just pretend and that Atsumu is going to pull away. That things got all fucked up and maybe won’t ever be the same. He could hardly eat dinner for all the knots in his gut. Hell, he’s not sure he’ll even be able to sleep tonight, what with all the new images of Atsumu—how he felt, how he sounded, the smell of his sweat and come—swirling like a vortex in his mind, making his secret phone collection almost worthless by comparison. 

With Ma across the house watching TV in the living room, and nothing better to do, Osamu takes out his phone and reads the group chat with Aran and their other school friends, but it’s so _boring._ He doubts any of them are having this kind of summer crisis.

The bedroom door opens, and Osamu looks up as Atsumu comes in, flushed and wet haired, a towel in his hand. Atsumu stands there, staring, and chewing his lip. 

Osamu puts down his phone. “What’s with ya?”

Atsumu sighs, shifting his feet. Then he squares his shoulders. He pushes the front of his pajamas down, and reveals his fully hard dick. Osamu’s brows shoot up to his hairline.

“Samu, can we…?” Atsumu asks, somehow bold and desperate at the same time.

Osamu’s belly swoops with a hungry need. He’s so cute. Fuck. Standing there all nervous. Atsumu experienced the most intense pleasure of his life, and now he’s hooked, and Osamu wants to _ruin him._

For now, Osamu puts his phone on the nightstand and pulls back the sheets in invitation, his hooded gaze knowing, the curl in his lip sharp. 

“Shut the door.”

  
  
  
  
  


**Author's Note:**

> I truly hope this satisfied your desires. If not, I'll gladly write you something else!


End file.
